We cannot better describe the Annulose animals than in the words of
Lamarck; he calls them,
“Animals with soft bodies, lengthened, worm-shaped, naked, or
inhabiting tubes, with the body divided into segments, or at least
transverse wrinkles, often without head, without eyes, and without
antennæ, unfurnished with articulated limbs, but the greater number
having, instead, small protuberances, bearing spines, and capable of
being retracted at pleasure, disposed in rows along the sides, though
not continued quite to the extremity of the body, and assuming various
forms. They have also red blood circulating by veins and arteries; this
separates them from the Worms, properly so called, which have white
blood. This colour of the blood is a singular fact, since the animals
are much less complex in their organization than the Mollusca, which
have colourless blood. The Class of Annulose animals has been separated
into three Orders, namely, _Annulata sedentaria_, which are fixed to
other substances; _Annulata antennata_, possessing antennæ, or feelers;
and _Annulata apoda_, without projecting members answering as feet,
serving solely to attach the animal to rocks, stones, &c.”
[Illustration: _Shells of various sedentary Annulose Animals._]
_ORDER ANNULATA SEDENTARIA_,
(_Sedentary Annulose Animals_.)
The creatures which form this order are generally found attached
to rocks, shells, &c. and are usually of small size. The engraving
represents a variety of species of these animals. Of the genus Serpula
there are many species, but as it is in general merely the shell
that is found in collections, they are but ill defined; some of the
species are found in almost all climates. The animal of the Serpula has
great power of contracting its body, but it never leaves its shell or
tube; this tube is gradually lengthened by the inhabitant, who always
occupies the most recently-formed portion of it; its _operculum_, the
lid with which it closes the opening of its tube, is very prettily
formed; it is something like the mouth-piece of a trumpet, but of
course not perforated, and it closes the opening with great accuracy.